As it turns out, Prince William will likely not be his brother's best man, because, well, there is no such thing as a best man at a royal wedding, according to Marlene Koenig, a British and European royalty expert.

"The best man or best men are officially called supporters," she tells Town & Country. "William will probably be Harry's supporter."

William broke protocol when he appointed Harry as his best man position at his wedding, according to The Guardian. Their father, the Prince of Wales, chose his brothers, Andrew and Edward, to be his supporter when he married Diana at St. Paul's Cathedral in 1981. And Prince Edward chose his brothers Charles and Andrew to be his supporters.

Best man or supporter, no doubt William will excel in assisting his brother, whom he is "delighted" for.

"We're very excited, delighted for them both. We're wishing them all the happiness in this very exciting time," the Duke of Cambridge told reporters on a recent visit to Finland. He jokingly added, "Personally, I hope it means he stays out of my fridge and will stop scrounging my food, which he's done for the last few years!"

Although William might not be Harry's best man, perhaps he'll help plan his bachelor party — just as Harry did for him. In the U.K., groomsmen typically celebrate a "stag weekend" with a few days worth of festivities.

According to Brides.com,"While details are scarce, Will's office confirmed that the Prince's party took place in late March (about a month before the wedding). Hosted by his brother, Prince Harry, at a country estate, the party included Will's close friends James Meade, Thomas van Straubenzee, and Guy Pelly."

As for who else will be in the wedding party? Koenig predicts everyone's favorite little royals — Prince George and Princess Charlotte, of course — could play a role. However, their mother, Catherine, Duchess of Cambridge, will not.

"It is very likely that Prince George and Princess Charlotte of Cambridge will be a page boy and a bridesmaid," she says.

No doubt, it will be an incredible occasion. A Kensington Palace spokesperson even released a statement saying the wedding will "be a moment of fun and joy that will reflect the character of the bride and groom."

"The couple of course want the day to be a special, celebratory moment for their friends and family," the spokesperson told journalists. "They also want the day to be shaped so as to allow members of the public to feel part of the celebrations too and are currently working through ideas for how this might be achieved."